President Trump and a Republican-led Congress tried and failed to repeal the Affordable Care Act. Now, they have to decide whether they want to work with it or sabotage it.

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Both Mr. Trump and congressional leaders acknowledged on Friday that they would not bring their repeal bill back for a vote any time soon. That means that, as Speaker Paul Ryan said, were going to be living with Obamacare for the foreseeable future.

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Mr. Ryan and Mr. Trump reiterated their criticisms of the law and set the stage for watching it collapse and blaming the Democrats for the aftermath. Ive been saying for the last year and a half that the best thing we can do politically speaking is let Obamacare explode, Mr. Trump said from the Oval Office. It is exploding now.

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Mr. Ryan said that Obamacares architects would be sad that the bill was allowed to live on, given what he described as its inevitable failure.

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In fact, Obamacare is not on the verge of explosion. Enrollment in its insurance marketplaces is steady, and several independent analyses suggest that insurance prices have stabilized after a sharp market correction this year. But the structures it set up to provide health insurance to middle-income Americans are vulnerable. Insurance companies have struggled to make money in the early years of the new markets, and many have backed out. Others remain tentatively committed and skittish.

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Mr. Trump will need to decide, quickly, whether his goal is to knock over the still-functioning markets, or help prop them up. If he decides to topple them, next year could be very messy.

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Insurers are making their decisions right now about whether to enter the markets for next year and about how much to charge their customers. Signals from the administration in the next few weeks about whether he will help or hurt them will almost certainly guide insurers choices.

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Fight a court case on subsidies?

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The biggest immediate decision concerns a court dispute between the House and the administration over subsidies to help low-income insurance buyers pay their deductibles and co-payments. The House has argued that the money for those subsidies was not properly authorized. The Obama White House fought the case. It is not clear whether Mr. Trumps lawyers will do the same. The availability of those subsidies, used by a majority of Obamacare customers, is critical for insurers in the markets.

Without the subsidies, all the insurers will lose some money, and many smaller carriers will face bankruptcy. If Mr. Trump does not fight the court case, the Obamacare markets in most states will unravel quickly, leaving millions without insurance options on his watch. Many of the beneficiaries are Trump voters.